Membrane Technology

To produce nitrogen from air, PCI uses hollow fiber membrane technology that allows oxygen to permeate the fibers, leaving high pressure nitrogen as the product.

 

Nitrogen Membrane

  

The membrane consists of a bundle of selectively permeable hollow fibers. The membrane separates nitrogen from atmospheric air by the principle of selective permeation across the membrane wall. The fast gases (oxygen, carbon dioxide and water vapor) permeate the membrane wall much faster than theslow gas (nitrogen).

 

The membrane separates the original gas mixture into two streams. One stream, the permeate, is concentrated in oxygen, carbon dioxide and water vapor. The other stream, the product, is high-pressure nitrogen. The permeate is vented to the atmosphere. The product, nitrogen, exits the downstream end of the membrane at near feed air pressure and is delivered to the end user or booster if further compression is required.

 

The purity of the product can be adjusted by changing the operation conditions. As Nitrogen flow rate is decreased, nitrogen purity increases and conversely, by increasing nitrogen flow, nitrogen purity is decreased. This is done via a flow / purity control valve at the discharge of the nitrogen stream after the flow meter and nitrogen analyzer, allowing finite control of flow or purity.

membrane diagram
   

Process Flow Diagram

  
Nitrogen membrane systems are on-site generators which produce nitrogen from atmosphere at the point of use. By producing nitrogen on-site, users can eliminate the logistics and cost associated with the liquid nitrogen supply chain of transports and pumpers. Operating cost savings of 50% or greater can be achieved by generating the product on-site.

 

These systems consist of 3 main components:

  1. Air Module: The Air Module consists of a diesel- or electrically-driven feed air compressor. The air compressor takes in ambient air and compresses it to 10-25 times atmospheric pressure. The compressed air passes through an oil separator and then is aftercooled, allowing water and oil vapors to condense and drop out from the air flow.
  2. Membrane Module: In the Membrane Module, the air pretreatment system employs a series of filters to clean and dry the air prior to exposure to the membrane separators. The clean compressed air travels through a reheater to keep any remaining moisture in the vapor phase. These are critical protective measures required for the longevity of the membrane fiber. The reheated air then passes through the membrane separators where the fast gases are ejected as waste and the nitrogen is collected and delivered at high pressure to the Booster Module.
  3. Booster Module: The Booster Module consists of a diesel- or electrically-driven booster compressor. Here, the nitrogen gas delivered from the membrane module is compressed to a higher pressure through 2-4 stages of compression depending on the system and requirement.


In the design and integration of the major components of our nitrogen membrane systems, PCI also takes into account the minor details as well to optimize the efficiency of the system. This can range from the class rating of engines for long term performance, the design of air pretreatment to minimize pressure drop for maximum nitrogen recovery efficiency and minimal maintenance, and to a quick and accurate air reheating system for stable control of output, just to name a few. Please feel free to contact any of our experts to learn more.